1. Field of the Invention
The field of the present invention method is the manufacture of tungsten carbide rings in general and in particular the method of manufacturing multi-element tungsten carbide rings from tungsten carbide plate.
2. Prior Art
For much of recorded history, jewelry has been manufactured from soft materials such as gold, platinum and silver. The most significant characteristic of these materials is that they are soft and are easily molded or machined. The problem that exists with jewelry manufactured from soft materials is that they are easily scratched or otherwise damaged.
In recent years, jewelry in the form of rings have been manufactured from hard material such as tungsten carbide or tantalum carbide which are much harder than the precious metals traditionally used to manufacture jewelry and will thereby prevent unwarranted defacement or damage to the jewelry. The problem with such materials is that, because of their hardness, they are extremely difficult to work with in order to produce attractive jewelry designs. As a result, the only method for utilizing these hardened materials in the manufacture of jewelry was to fabricate parts from powdered metals which have been solidified into a predetermined shape for handling and which possessed the properties necessary for the finished part. The prior art discloses the use of compression molds to form the powdered metals into the predetermined shapes that would be required for the finished part. Compression molding can require pressure in the range of 5-100 tons per square inch. However, although the use of compression molds will create a solid blank of powdered metal in a predetermined form, the compacted blanks must be sintered to recrystalize the material which will provide the enhanced hardness.
The use of compression molds to form the initial ring blank and the use of a sintering process to produce the hardened material are disclosed in U.S. Pat. Nos. 8,061,033; 7,761,996 and 6,641,640. Although the combined use of compression molds to form a solid initial blank and the application of a sintering process to harden the material is well-known, the problems inherent in these processes are also well-known. A substantial disadvantage of powder metallurgical shaping processes is that the moldings are limited to comparatively simple external shapes. Another known powder metallurgical process is powder injection molding. The main problem with powder injection molding is the need to remove the binder material used in the sintering process. A further disadvantage relates specifically to the manufacture of jewelry. The need to create the initial forms of the blank in a compression mold defines the ultimate sizing of the ring. Since a manufacturer is required to produce a full range of ring sizes, use of a compression molding process would require multiple molds for each design thereby increasing the cost of manufacturing the rings.
The present invention method overcomes the disadvantages inherent in the manufacturing methods disclosed by the prior art by producing the tungsten carbide annular blanks needed to produce multi-element jewelry rings directly from finished tungsten carbide plate. The prior art limits the structure of jewelry rings to a single annular band of tungsten carbide which is then faceted to adapt the tungsten carbide band to receive ornamentation in the form of inlays or mountings for gems. The present invention provides a method whereby jewelry rings may be constructed of a plurality of annular elements, one or more of which is composed of tungsten carbide. This greatly expands the spectrum of ornamentation that can be created.
The present invention method negates the need to use the restrictive process of using compression molds to form a solid blank of powered metal in a predetermined form. The present invention method employs electrical discharge machining (EDM) to produce the tungsten carbide elements that will be used to create a jewelry ring. EDM is a controlled metal-removal process that is used to remove metal by means of electric spark erosion. In this process, an electric spark is used as the cutting tool to cut or, in effect, erode a workpiece to produce the finished part to a desired shape. The metal-removal process is performed by applying a pulsating electrical charge of a high-frequency current through an electrode to the workpiece. This process permits the removal of very tiny pieces of metal from the work piece at a controlled rate.
A limitation to the use of electrical discharge machining is that it can operate only with materials that are electrically conductive. However, since tungsten carbide is composed primarily of tungsten, it is an electrically conductive material. During the process, the workpiece and the electrode are submerged in a dielectric fluid which is used as a coolant and to flush away removed material. The present invention employs both ram EDM and wire EDM apparatus. Ram EDM uses a shape tooling electrode to facilitate the machining process which in this case is used to drill or otherwise form the interior surface of the annular blank being made from the tungsten carbide plate. When using a computerized numerically controlled plotter, wire EDM is used to cut the annular blank from the tungsten carbide plate. This will produce an annular tungsten carbide blank having the uniform thickness necessary to produce the tungsten carbide elements employed in the jewelry rings manufactured pursuant to the present invention method. The electrical discharge apparatus uses a fine metallic wire that acts as a cutting electrode to accurately cut the annular blank from the tungsten carbide plate. Once a plurality of annular blanks are cut from the tungsten carbide blank, the inner and outer surfaces of respective blanks may be machined to adapt the annular blanks to be assembled into a multi-element jewelry ring in a manner that substantially improves over the methods disclosed by the prior art to produce jewelry rings composed in whole or in part of tungsten carbide.